Fuel gauge/sending unit issue

1996 370 DA
The port fuel gauge was not working, i replaced with a band new gauge still no movement on needle so i figured it was the sending unit...picked up a new sending unit, installed it, flipped the start switch to see the needle move but nothing so i turned the starboard switch on to see that gauge move but no movement. i unplugged the ground wire on the new port sending unit, flipped the starboard switch on and that needle went backward well below E. what's going on? neither gauges work now! HELP

Go to the gauge, jump the wires together, gauge should read full . If not you have a wiring issue

which wires? there are several behind the gauge.

Here's a how to on this with pictures. https://www.sailmagazine.com/diy/test-replace-fuel-gauge-sending-unit

On the back of the gauge, the wires you'll be concerned with are labled +, - and G If you jump - to the G, gauge should go to full.

On the sending unit, it you pull the center wire, and ground it (there will be another wire attached to the top frame, or tank, gauge should read full.